Have you ever tuned into your local radio station and heard the travel news being read out from the 'eye in the sky' - a presenter checking out the traffic from an aircraft high over the area concerned? Have you ever stopped to think how that is done? Well Wireless Waffle is here to help explain it all.

There is no denying that it would be very easy for any radio station to pretend to have a traffic plane or helicopter by playing sound effects in the background whilst the travel news was read out. However, there are some real benefits about doing it properly, not least it is possible to find out how the traffic is flowing as and when problems occur instead of waiting for listeners to phone in news (which can be unreliable) or for the local police or traffic department to let you know what's happening. But that doesn't mean that the aircraft in question can necessarily see all the problems in an area and in some cases, it is not possible to fly over certain areas due to airspace restrictions (for example, it would not make sense for a 'traffic plane' to be buzzing around a major airport, stopping commercial airliners from landing!)

What happens, therefore, is that there is someone on the ground who collates traffic information in the normal way (eg through listeners or the police) and then relays this information to the man in the aircraft. The plane (or chopper) can then visit some of the travel hotspots and see what is happening and if, along the way, they see other problems that haven't been reported, they can update the person on the ground. This means that, in general, travel news from an aircraft is more accurate and up-to-date than travel news from a regular travel studio.

From the technology perspective, there is lots of radio used (hence the Wireless Waffle interest). For starters, the pilot will be communicating with various air traffic controllers on the VHF aeronautical band (117.975 to 137.000 MHz).

Next, there is a need for the person on the ground, including the presenter in the radio studio, to be able to communicate with the presenter in the aircraft - the 'uplink'. Typically this is done via a simple VHF or UHF PMR frequency (in the UK try listening around 141.000 to 141.500 MHz and 455.000 to 455.500 MHz). As well as passing travel news to the airborne presenter, this frequency is also often used as the 'cue', providing a live feed of the station on which the travel news is to be broadcast so that the airborne presented knows when to start reading the news.

Finally there is a the link from the airborne presenter to the ground - the 'downlink'. This is usually (but not always) a slightly higher quality link than the uplink as the audio is going to be broadcast. In the UK, these links are usually at UHF (try between 467.250 and 469.900 MHz). As they are transmitted from the aircraft, despite being low power, they can often be heard over a wide area.

If the aircraft is providing travel news for a wide area, more than one up and/or downlink might be used for the different areas, depending on whether or not frequencies which can be used over a wide area are available.

In some countries, the presenter uplink and downlink are also in the aeronautical VHF band (this is the case, for example, in Malta), and the frequencies use do vary significantly between countries. If you are in an area where the local radion station has a travel plane or helicopter, why not have a tune around and see what you can find and post a comment to let us all know.

My couple of previousposts concerning reception of BBC World Service English language programmes on short-wave in Europe led me to wondering whether there wasn't a more elegant solution to the problem of identifying which frequencies to tune to at any given time of the day.

As it happens, every 6 months, the majority of international broadcasters get together and sit down to negotiate and co-ordinate their HF frequency usage for the coming 6 months at a conference known as the High Frequency Co-ordination Conference. The resulting plans (know as the Winter and Summer seasons) are published on the web. So with a little ingenuity and a few spare hours, Wireless Waffle proudly presents:

It works like this: You can select broadcasts in a particular language, or by a particular broadcaster in which case you will be presented with a list of transmissions currently on-air (or on-air at a time you select) today for that broadcaster together with a map of the world showing where those frequencies are being transmitted from. Using this list you can try tuning to those transmitters most local to you (or for fun those more distant) to see what you can hear.

Alternatively you can select a broadcaster AND a language in which case you will receive a list of all frequencies and times for that broadcaster in that language for today, highlighting those which are currently on-air with a map showing where those frequencies which are on-air are being broadcast from. It sounds more complicated than it is - go and try it!

To help, regions in daylight and darkness are also shown. Generally speaking if you are in an area of darkness, look for stations also in darkness which are transmitting on low frequencies (say 10 MHz - 10000 kHz - or less). If you are in an area of daylight, look for frequencies also in daylight (over 10 MHz or so).

Further to last month's comments on receiving BBC World Service English in Europe, we've been testing out some of the frequencies that were suggested from the Wireless Waffle HQ in southern Great Britain. At all times checked, at least one BBC English frequency was available and at some times, several were audible. The list below gives the times checked and the frequencies that were audible. A simple rating system has been employed with one * representing poor reception, ** representing reasonable reception and *** representing a nice strong signal.

Reception will change from day-to-day and month-to-month so this list may not remain accurate indefinitely but it shows what can be achieved with a little effort. This list will be updated from time-to-time so check back occasionally if you're missing your Lily Bolero!

The end of an era is afoot (or at hand, whichever you prefer). Earlier this year the BBC World Service announced that it has stopped transmission of its English service to Western Europe. No longer will the strains of 'Lili Bolero' or 'Big Ben' be heard on the hour in France, Germany or anywhere east of Moscow. Or will it?

The BBC claim that certain frequencies destined for other parts of the world, notably Western Russia, may still be audible in some parts of Europe for those who absolutely insist on listening to the news from London with loads of hiss, crackle, distortion and fading. But to what extent is this possible? Is World Service short wave reception in Western Europe gone forever or is there still the possibility to listen in?

A scan of the material published by the BBC shows that there are still plenty of transmitters on-air carrying BBC World Service English (albeit different regional variants), pretty much around the clock. The question therefore is whether any of them are audible in Europe.

Whether or not a short wave transmission is audible in any given place depends on a number of factors including the transmission frequency, the time of day (in particular whether the path between transmitter and receiver is in daylight or darkness), the distance between transmitter and receiver and the intended target for the transmission. Take for example the World Service English transmission to Africa from its transmitter site on Ascension Island in the South Atlantic. At various times during the (European) day, this is on a frequency of 17830 kHz. This high frequency propagates well through areas in daylight and the direction of the transmission is roughly the same as the direction from Ascension to most of Europe. The distance between Ascension and Europe requires the transmission to hop into and out of the ionosphere a couple of times but on a normal day, if both ends of the path are in daylight, this should work. Barring any co-channel or strong adjacent channel interference, therefore, the BBC transmission from Ascension should be (and indeed is) audible in Europe.

During the hours of darkness, low frequencies (the 48, 41 and 31 metre band for example) tend to propagate well, whereas during the day, higher frequencies (the 25, 19 and 16 metre bands) will fare better. Taking all this into account, it should be possible to construct a schedule of which BBC World Service English programmes are most likely to be heard in Europe. Of course this will change twice a year as the winter and summer schedules take effect, but the principles should hold true.

With that in mind, here is the Wireless Waffle guide to receiving BBC World Service English in Europe on short wave. The frequencies shown are those that have the best chance of being received in Europe but which are directed to other regions (thus the programming material may not necessarily be appropriate). No account of possible interference has been made (for example it is known that the BBC frequency of 17640 kHz suffers strong adjacent channel interference in Europe from Africa No. 1 on 17630 kHz and China Radio International on 17650 kHz). Other frequencies have strong co-channel and adjacent channel interference too so it's definitely a case of 'if at first you don't succeed, try, try, try again'.

Note that these frequencies were taken from the Winter 2008/9 broadcast schedule and may be very out of date if you are reading this in 2013! Also, not all frequencies are on for the whole period (some are not daily either), so you will have to tune around between the ones listed to find the best possible reception for the time you are listening.